U.S. patent number 4,462,037 [Application Number 06/385,955] was granted by the patent office on 1984-07-24 for ink level control for ink jet printer.
This patent grant is currently assigned to NCR Corporation. Invention is credited to Richard G. Bangs, Jacob E. Thomas.
United States Patent |
4,462,037 |
Bangs , et al. |
July 24, 1984 |
Ink level control for ink jet printer
Abstract
The level of ink in a reciprocating reservoir is automatically
controlled for both printing and non-printing conditions. The
reciprocating motion creates forces to cause the ink to move back
and forth between the reciprocating reservoir and a main reservoir
and a pump maintains the ink at one level during printing. The pump
controls the direction and flow of ink moving between the
reservoirs by continuous operation during printing and the ink is
allowed to rise in the first-mentioned reservoir during
non-printing.
Inventors: |
Bangs; Richard G. (Ithaca,
NY), Thomas; Jacob E. (Ithaca, NY) |
Assignee: |
NCR Corporation (Dayton,
OH)
|
Family
ID: |
23523585 |
Appl.
No.: |
06/385,955 |
Filed: |
June 7, 1982 |
Current U.S.
Class: |
347/85;
347/89 |
Current CPC
Class: |
B41J
2/17566 (20130101) |
Current International
Class: |
B41J
2/175 (20060101); G01D 015/18 () |
Field of
Search: |
;346/75,14R,14PD |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Miller, Jr.; George H.
Attorney, Agent or Firm: Cavender; J. T. Hawk, Jr.; Wilbert
Muckenthaler; George J.
Claims
We claim:
1. Means for controlling the level of ink in an ink jet printing
system comprising a
first reservoir containing a quantity of ink, a
second reservoir containing a quantity of ink,
means providing an ink supply line and an ink return line
connecting the first and the second ink reservoirs,
means operably associated with said second reservoir for ejecting
ink in droplet form, and
means associated with the ink return line for causing continuous
flow of ink from the second reservoir to the first reservoir and
establishing a first ink level in the second reservoir adjacent the
ink return line during operation of the printing system and for
allowing flow of ink from the first to the second reservoir and
establishing a second ink level in the second reservoir adjacent
the ink ejecting means during non-operation of the printing
system.
2. The subject matter of claim 1 wherein the ink flow causing means
comprises a circulating pump operating during printing operation to
establish said first ink level and non-operating to permit flow of
ink through the ink supply line to establish said second ink
level.
3. The subject matter of claim 1 wherein the ink ejecting means is
a tubular transducer.
4. The subject matter of claim 1 wherein the first reservoir is a
stationary reservoir and the ink flow causing means is a pump
operating continuously during operation of the printing system.
5. The subject matter of claim 4 wherein the second reservoir is a
movable reservoir carrying the ink ejecting means.
6. The subject matter of claim 4 including means associated with
the ink supply line for damping the flow of ink to the second
reservoir.
7. The subject matter of claim 4 wherein the ink supply line and
the ink return line are flexible tubes allowing movement of the
second reservoir in relation to the first reservoir.
8. Ink level controlling means comprising a
first reservoir containing a quantity of ink, a
second reservoir containing a quantity of ink,
means connecting the first and second reservoirs and providing ink
supply and ink return lines therebetween, and
pump means operably associated with the ink return line for causing
continuous flow of ink from the second to the first reservoir when
the ink is at one level in the second reservoir adjacent the ink
return line during printing conditions and for allowing flow of ink
from the first to the second reservoir to pursue a higher level in
the second reservoir during non-printing conditions.
9. The subject matter of claim 8 including a transducer operably
associated with and carried by said second reservoir for ejecting
ink therefrom in droplet form.
10. The subject matter of claim 8 wherein said first reservoir is
stationary and said second reservoir is movable and includes an
elongated ink feed tube therein.
11. The subject matter of claim 10 wherein the ink supply line and
the ink return line are flexible conduits permitting movement of
the second reservoir relative to the first reservoir.
12. The subject matter of claim 10 including means associated with
the ink supply line for restricting flow of and for filtering ink
traveling from the first to the second reservoir.
13. The subject matter of claim 10 wherein the ink flow causing
means comprises a circulating pump operating during printing
conditions when the ink is at said one level and non-operating to
permit flow of ink through the ink supply line to pursue said
higher level.
14. In an ink jet printer having a first reservoir of ink and a
second reservoir of ink movable in relation to the first reservoir,
means connecting the first and second reservoirs to provide an ink
supply line and an ink return line therebetween, the improvement
comprising
means for causing the second reservoir to move in reciprocating
manner during printing conditions enabling flow of ink into the
second reservoir and attain a predetermined level therein adjacent
the ink return line connected thereto, and
means operably associated with the ink return line causing
continuous flow of ink from the second reservoir to the first
reservoir while maintaining such predetermined level under printing
conditions and enabling the level of ink to pursue a higher level
in said second reservoir during non-printing conditions.
15. In the printer of claim 14 including a transducer operably
associated with and carried by said second reservoir for ejecting
ink therefrom in droplet form.
16. In the printer of claim 14 wherein the operably associated
means is a circulating pump operating during printing conditions to
maintain said predetermined level and non-operating to permit flow
of ink through the ink supply line to pursue said higher level.
17. An ink jet printer comprising a
first reservoir containing a supply of ink, a
second reservoir connected with said first reservoir,
means for moving said second reservoir in reciprocating manner
during operation of the printer,
means operably associated with the second reservoir for ejecting
ink in droplet form, and
means for moving said first reservoir downwardly relative to said
second reservoir for establishing one ink level in the second
reservoir during operation of the printer and for moving the first
reservoir upwardly relative to the second reservoir for
establishing another ink level in the second reservoir during
non-operation of the printer.
18. The ink jet printer of claim 17 wherein the ink ejecting means
is a tubular transducer.
19. The ink jet printer of claim 17 including a flexible ink supply
line connecting the first and the second reservoirs and means
associated with the ink supply line for damping flow of ink to the
second reservoir.
20. The ink jet printer of claim 17 wherein the means for moving
the first reservoir is effective to lower the first reservoir to
establish in said second reservoir said one ink level at a height
above the connection thereof with said first reservoir and to raise
the first reservoir to establish in said second reservoir said
another ink level at a height substantially adjacent the ink
ejecting means.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
Ink Evaporation Prevention Means For Ink Jet Printer, U.S. Pat. No.
4,412,233, issued to J. E. Thomas and J. K. McKnight on Oct. 25,
1983.
Ink Level control For Ink Jet Printer, co-pending application Ser.
No. 385,965, filed June 7, 1982, invented by Jacob E. Thomas, and
assigned to NCR Corporation.
Ink Control For Ink Jet Printer, U.S. Pat. No. 4,418,353, issued to
J. E. Thomas on Nov. 29, 1983.
Ink Control For Ink Jet Printer, co-pending application Ser. No.
385,967, filed June 7, 1982 invented by Jacob E. Thomas, and
assigned to NCR Corporation.
BACKGROUND OF THE INVENTION
In the field of non-impact printing, the most common types of
printers have been the thermal printer and the ink jet printer.
When the performance of a non-impact printer is compared with that
of an impact printer, one of the problems in the non-impact machine
has been the control of the printing operation. As is wellknown,
the impact operation depends upon the movement of impact members,
such as print hammers or wires or the like, which are typically
moved by means of an electromechanical system and which may, in
certain applications, enable a more precise control of the impact
members.
The advent of non-impact printing, as in the case of thermal
printing, brought out the fact that the heating cycle must be
controlled in a manner to obtain maximum repeated operations.
Likewise, the control of ink jet printing, in at least one form
thereof, must deal with rapid starting and stopping movement of the
ink fluid from a supply of the fluid. In each case of non-impact
printing, the precise control of the thermal elements and of the
ink droplets is necessary to provide for both correct and
high-speed printing.
In the matter of ink jet printing, it is extremely important that
the control of the ink droplets be both precise and accurate from
the time of formation of the droplets to depositing of such
droplets on paper or like record media and to make certain that a
clean printed character results from the ink droplets. While the
method of printing with ink droplets may be performed in either a
continuous manner or in a demand pulse manner, the latter type
method and operation is disclosed and is preferred in the present
application when applying the features of the present invention.
The drive means for the ink droplets is generally in the form of a
well-known crystal or piezoelectric type element to provide the
high-speed operation for ejecting the ink through the nozzle, while
allowing time between droplets for proper operation. The ink nozzle
construction must be of a nature to permit fast and clean ejection
of ink droplets from the print head.
In the ink jet printer, the print head structure may be a multiple
nozzle type with the nozzles aligned in a vertical line and
supported on a print head carriage which is caused to be moved or
driven in a horizontal direction for printing in line manner.
Alternatively, the printer structure may include a plurality of
equally-spaced horizontally-aligned single nozzle print heads which
are caused to be moved in back-and-forth manner to print successive
lines of dots in making up the lines of characters. In this latter
arrangement, the drive elements or transducers are individually
supported along a line of printing.
In a still different structure, the nozzles are spaced in both
horizontal and vertical directions, and the vertical distance
between centers of the ink jets equals the desired vertical
distance between one dot and the next adjacent dot above or below
the one dot on the paper. The horizontal distance is chosen to be
as small as mechanically convenient without causing interference
between the actuators, reservoirs, and feed tubes associated with
the individual jets. The axes of all jets are aligned approximately
parallel to each other and approximately perpendicular to the
paper. Thus, if all nozzles were simultaneously actuated, a sloped
or slanted row of dots would appear on the paper and show the dots
spaced both horizontally and vertically. In order to produce a
useful result consisting of dots arranged as characters, it is
necessary to sweep the ink jet head array back and forth across the
paper, and actuate each individual nozzle separately when it is
properly located to lay down a dot in the desired position. A
vertical row of dots is created by sequentially actuated the
nozzles rather than simultaneous actuation, the latter being the
preferred practice in the more common nozzle arrangements.
A further observation in ink jet printers is that previous and
current designs for drop-on-demand ink jet print heads are
sensitive to the ingestion of air into or the presence of air in
the supply of ink. Even a small air bubble can interrupt or fault
the performance of transducers or like devices that expel ink
droplets from a nozzle by means of pressure pulses created within
an ink-filled chamber or channel.
The use of a fast-action valve or like device to control the flow
of ink to a single ink jet printing nozzle is known in specific
applications, but in certain cases, the concept and
heretofore-known structure has been considered costly and
impractical. Additionally, the supply of ink to a plurality of ink
jet nozzles may be controlled by means of a single control device
wherein the nozzles are connected to a common manifold and ink
droplet ejection is accomplished by momentarily increasing the
pressure in the manifold.
After the droplets of ink have been ejected from the nozzles, the
ink is replenished thereat from a remote supply by the capillary
action of the meniscus at the end of the nozzle. In certain of the
control devices and arrangements, it has been found that some
difficulties arise from the capillary action refill or replenish
process and there are adverse effects on the performance and
reliability of such printers.
In normal operation of an ink jet print head, it is well-known that
a negative meniscus of ink should be maintained at the nozzle, that
the relative levels of ink in the various parts or areas of the
system have an effect on the printing operation, and further, that
the movement of the several printer elements affects the flow of
ink during the printing cycle.
Representative documentation in the field of ink control means for
ink jet printers includes U.S. Pat. No. 3,737,914, issued to C. H.
Hertz on June 5, 1973, which discloses a liquid jet recording
system in which an electrically-conductive fluid is
pressure-ejected through capillary nozzles to form jets directed
toward a recording sheet and wherein a group of the jet nozzles are
mounted in a common plane and are movable periodically in
side-to-side direction.
U.S. Pat. No. 4,042,937, issued to F. J. Perry et al. on Aug. 16,
1977, discloses an ink supply system for an ink jet head which
includes an inlet valve connecting a pump in the line from a
reservoir to the head and an outlet valve connecting an outlet from
the head to the reservoir. At time of shut off, the inlet valve is
closed with the outlet valve open to create a negative pressure in
the head.
U.S. Pat. No. 4,079,384, issued to R. Takano et al. on Mar. 14,
1978, discloses an ink liquid supply system having an ink
cartridge, an ink reservoir, a pump and a cross valve in the supply
line.
U.S. Pat. No. 4,153,902, issued to Y. Kanayama on May 8, 1979,
discloses an ink liquid supply system wherein a subtank is
interposed between an ink reservoir and a pump in the supply line.
A valve and a pair of filters are also provided in the line.
SUMMARY OF THE INVENTION
The present invention relates to ink jet printers, and more
particularly, to control means which includes a pump provided in
one line between an ink supply tank and a second tank carrying an
ink jet nozzle. The ink supply system provides a main reservoir
which is stationary and vented to the atmosphere, and a local
reservoir which is carried on a carriage movable in back-and-forth
manner along a print line relative to paper or like record media.
The local reservoir has at least one print head supported from and
carried therewith in reciprocating manner during the printing
operation.
The ink is caused to flow from the main reservoir through a tube
having a constriction device for preventing or minimizing surges of
ink into the local reservoir. A filter is also included in the
constriction device for continuous filtration of the ink. An ink
return line from the local reservoir to the main reservoir includes
a fluid pump to cause a continuous flow of ink therebetween to
maintain the ink level in the local reservoir at a certain and
desired level.
The apparatus and arrangement provides for controlling and
maintaining the level of ink slightly above the inlet height of the
return line or tube when the carriage is reciprocating in a
printing condition or operation, and then allowing the ink level to
rise to the level of the ink in the main reservoir or approximately
to the height of the ink jet print head nozzle when the print head
is idle or in the non-printing condition.
A modification in the main reservoir and the reciprocating local
reservoir arrangement includes apparatus for causing the main
reservoir to be moved in a vertical direction to provide the
pumping action between the reservoirs and to maintain the desired
level of ink.
In view of the above discussion, the principal object of the
present invention is to provide means permitting controlled amount
of ink to flow between separate reservoirs in an arrangement to be
used for marking or printing on record media.
Another object of the present invention is to provide means for
controlling flow of ink from a supply thereof to at least one ink
jet nozzle.
An additional object of the present invention is to provide means
for controlling flow of ink between a main reservoir and a
reciprocating reservoir carrying an ink jet print head.
A further object of the present invention is to provide a main
reservoir and a reciprocating reservoir of ink along with pumping
means therebetween for maintaining the ink in the reservoirs at
predetermined levels during both printing conditions and
non-printing conditions.
Another object of the present invention is to provide a main
reservoir and a reciprocating reservoir wherein the main reservoir
is caused to be moved in up-and-down manner to provide pumping
action for maintaining the ink in the reservoirs at predetermined
levels.
Additional advantages and features of the present invention will
become apparent and fully understood from a reading of the
following description taken together with the annexed drawing.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a diagrammatic view, partly in section, of a printing
system incorporating the subject matter of the present invention;
and
FIG. 2 is a modification of the printing system of FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As seen in FIG. 1 of the drawing, an ink reservoir 10 contains a
supply of printing ink 12 which is sufficient for printing in
excess of several million characters. The reservoir 10 has a
filter-type vent 14 suitably disposed in the top thereof for access
to the atmosphere. A length of flexible tubing 16 is connected at
one end 18 thereof to the outlet 20 of the reservoir 10 and is
connected at the other end 22 thereof to an inlet 24 of a
constricting-type device 26 which is formed of suitable material to
dampen or impede the flow of ink from a main or remote reservoir 10
to a second or local reservoir 28. The reservoir 28 also has a
filter-type vent 29 disposed in the top thereof. A second flexible
tube 30 is connected at one end 32 thereof to an outlet 34 of the
device 26 and is connected at the other end 36 to an inlet 38 of
the reservoir 28. The tubes 16 and 30 provide an ink supply
passageway for flow of ink from the main reservoir 10 to the device
26 and from such device to the local reservoir 28.
A return path for the flow of ink is provided from the reservoir 28
to the reservoir 10. A flexible tube 40 is connected at one end 42
thereof to an outlet 44 (above the inlet 38) of the reservoir 28
and is connected at the other end 46 thereof to the inlet 48 of a
pump 50 which is suitable for causing ink to flow from the
reservoir 10 to the reservoir 28 in continuous manner under
printing operation or conditions. The pump 50 may be a common and
well-known, electrically energized, type for causing a negative
pressure in the reservoir 28 and producing a continuous flow
between the two reservoirs 10 and 28 in the arrangement for
establishing the proper ink level at the proper time for printing
operations. Actuation of the pump 50 during printing operations
establishes a level for the ink in reservoir 28, which is a
condition required for proper operation of the ink jet printer. A
flexible tube 56 is connected at one end 58 thereof to the outlet
60 of the pump 50 and is connected at the other end 62 thereof to
an inlet 64 of the main reservoir 10.
The secondary or local reservoir 28 is secured to or supported from
a movable carriage 66 which causes the reservoir to be moved in a
reciprocating manner in a direction to and from the observer, as
viewed in the drawing. A feed tube 68, of a length and extending
from near the bottom of the reservoir 28 to a height which is above
the normal level of ink in the main reservoir 10, includes an upper
outlet portion 69 which extends through a wall portion or grommet
70 of the reservoir 28 to an ink jet print head 72. The several
tubes utilized in the system may be made of Tygon (a polyvinyl
chloride material manufactured by The Norton Chemical Company).
The print head 72 includes a body portion 74 of cylindrical form
having a glass tube or glass-lined passageway 76 through the body
portion for receiving and connecting to the feed tube portion 69
and terminating in a nozzle 78 for ejecting a droplet 80 of
printing ink to be applied to record media 82, which media may be
in the form of paper or the like and supported in suitable manner
around a drum or from a platen (not shown).
The print head 72 may be of a type as disclosed in Arndt U.S. Pat.
No. 3,832,579, appropriate for and commonly used in ink jet
printing operations, and which includes a piezoelectric device or
tubular type transducer 84 for causing ejection of the ink droplets
80, either in synchronous or asynchronous manner, from the print
head nozzle 78. The ink droplets 80, so produced from the nozzle
78, are essentially the same or constant in size and are normally
ejected at a constant velocity. Leads 86 and 88 are appropriately
connected to the print head 72 for actuating the transducer 84 so
as to cause ejection of the ink droplets 80 in well-known
manner.
In the operation of the printing system, the pump 50 is turned on
along with the printer and the reservoir 28 is caused to be moved
by the reciprocating motion of the carriage 66 in a printing
condition wherein the motion of the carriage creates forces which
tend to cause the ink to be moved back and forth, or in a somewhat
defined supply-and-return cycle between the reservoirs 10 and 28.
Prior to printing operation, i.e. when the reservoir 28 along with
the print head 72 are rapidly moving or reciprocating in the
back-and-forth direction, the pump 50 is called into operation and
causes the level of ink 12 in the local reservoir 28 to be lowered
and then maintained approximately at or slightly above the level
indicated at 90, which is slightly above the height of the outlet
44 and the end 42 of the tube 40, and which level is substantially
below the level 92 of the ink 12 in the main reservoir 10. The pump
50 thus provides a continuous circulating flow of ink 12 between
the two reservoirs 10 and 28 during printing operations and in a
manner wherein the flow of ink is dampened or reduced and the ink
is also continuously filtered by the device 26. An added feature
may include an ink level sensor or automatic level sensing device
(not shown) which may be connected inside the local reservoir 28
and used to control the pump 50 in an arrangement to allow the
proper level of ink during printing operation or conditions, but
would turn the pump off at a low ink level condition.
When the printing operation ceases or when the reservoir 28 along
with the print head 72 are not moving or reciprocating, as in the
non-printing or rest condition, the ink 12 in the local reservoir
28, by reason of gravity, slowly rises above the height of the
outlet 44 and may rise to a level indicated at 94, corresponding
generally with the level 92 of ink 12 in the main reservoir 10 and
approximately to or slightly below the height of the print head 72.
In this respect, the ink levels 92 and 94 tend to be equalized
through the ink supply tubes 16 and 30 and since the level of ink
12 in the reservoir 28 is above the outlet 44 thereof, the pump 50
is ineffective in a non-running condition and due to the increasing
level of ink in the reservoir 28, the gravitational flow of ink 12
is in the direction from the main reservoir 10 to the local
reservoir 28 for substantially filling the latter.
It is seen that the system provides for simple pumping means with
two distinct levels of ink in the ink reservoir 28 directly
associated with the operation of and directly supplying the ink jet
print head 72. The idle or non-printing level at 94 in the local
reservoir 28 is approximately at print head height and the
operating or printing level at 90 is about two inches lower or at
approximately the height of the outlet 44 and of the return tube
40. The motion of the carriage 66, on which the print head 72 and
the reservoir 28 are mounted, along with the continuous operation
of the pump 50 provide the driving force to pump the ink 12 from
the main reservoir 10 to the local reservoir 28 and additionally,
the pump 50 ensures that the ink 12 moves only in the proper
direction during certain conditions, all in a manner and
arrangement wherein the ink level control is considered to be
automatically controlled during both idle or non-printing periods
and operating or printing periods.
It is seen that the constriction device 26 in the supply line to
the local reservoir 28, the pump 50 in the return line to the main
reservoir 10, and the location of the inlet 44 for the return tube
40 all provide for and prevent unwanted surges in the ink 12 which
are caused by motion of the carriage 66. If such surges were
allowed to occur, the pressure in the reservoir 28 would suddenly
change and cause ink to be unintentionally ejected from the nozzle
78 or to cause air to be ingested therein.
In an alternate system or modification of the above-described
arrangement, the pump has been omitted (as seen in FIG. 2) along
with the return line which included the flexible conduits or tubes
40 and 56 connected to the local reservoir 28 and to the main
reservoir 10 for carrying ink 12 therebetween, as seen in FIG. 1.
Since the same reference numerals are used for the identical
elements in FIG. 2 as were used in FIG. 1, the complete detailed
description is not repeated. In the alternate system of FIG. 2,
means is provided for raising and lowering the main reservoir 10 in
relation to the local reservoir 28 and thereby establish the two
levels of ink in the local reservoir.
The particular means employed for raising and lowering the
reservoir 10 may be a simple hydraulic lift mechanism or a solenoid
operated device, such as diagrammatically illustrated at 106, which
mechanism or device is capable of operating in a raising and
lowering range of several centimeters. The reservoir 10 is raised
or elevated to the position shown in FIG. 2, and under idle or
non-printing conditions, the level of the ink 12 is approximately
at ink jet nozzle 72 height. Under operating or printing
conditions, the main reservoir 10 is lowered by operation of the
mechanism or device 106 so that the level 92 of ink 12 therein
corresponds generally to the ink level 90 in the local reservoir
28. Thus, the level of ink in the moving reservoir 28 will descend
to a predetermined point and settle or stop at that point. In
similar manner as mentioned above, when the carriage 66 and the
reservoir 28 are not moving, the ink level will slowly rise by
flowing through the supply tubes 16 and 30 until the two reservoirs
10 and 28 have approximately equal ink levels, or rather, the ink
12 in the two reservoirs 10 and 28 is at approximately the same
height.
It is thus seen that herein shown and described is an ink jet
printing system which includes means to control the level of the
ink during both printing and non-printing conditions. A supply line
and a return line for the ink are connected between a stationary
reservoir and a reciprocating reservoir, and the ink is caused to
flow by movement of the reciprocating reservoir and by action of a
pump to effect continuous circulation and attain one ink level in
the local reservoir during printing and to allow the ink to rise to
another level therein when idle or non-printing. The alternate or
modified system also utilizes movement of the reciprocating
reservoir to cause flow of ink, and an elevator mechanism controls
the level of ink in the two reservoirs during printing and
non-printing. When the main reservoir is being lowered prior to
printing, the flow of ink is in the direction from the local
reservoir to the main reservoir, whereas raising the main reservoir
causes flow of ink therefrom to the local or reciprocating
reservoir. The apparatus of the present invention enables the
accomplishment of the objects and advantages mentioned above, and
while a preferred embodiment has been disclosed herein, along with
a modification thereof, other variations may occur to those skilled
in the art. It is contemplated that all such variations not
departing from the spirit and scope of the invention hereof are to
be construed in accordance with the following claims.
* * * * *